Animals, including humans, explore the environment using active strategies that involve moving their sensors (fingers, eyes). An excellent example of this type of behavior is active whisking in rodents. During active whisking, rats move their whiskers in stereotyped ways making contact with objects (active touch) to identify them and to explore the environment. An important problem is that sensory systems in the brain must detect the neural activity related to active touch by distinguishing it from the activity caused by moving the whiskers. The whiskers transmit this sensory information through primary sensory relay cells in the trigeminal complex, which produce two major ascending and contralateral pathways. One innervates the thalamus, leading primarily to the neocortex in the forebrain (trigeminothalamic), and the other innervates the deep layers of the superior colliculus in the midbrain tectum (trigeminotectal). The role of these two ascending pathways in the detection of active touch signals during exploratory whisking is poorly understood. We propose that the superior colliculus is a major sensory relay that serves to detect touch signals during exploratory behavior by differentiating movement-related and contact-related activity. Therefore, in agreement with its well-known role in orienting to novel stimuli, the superior colliculus is an essential component of the sensory circuitry responsible for the detection of sensory stimuli during active exploration. There are three goals in this project. The first goal is to determine the response properties of superior colliculus cells during whisking movement and touch. The second goal is to determine the role of superior colliculus afferents in driving and/or modulating the whisking responses. The third goal is to characterize the activity and response properties of superior colliculus cells as animals actively move their whiskers and detect behaviorally relevant sensory stimuli during exploratory behavior. The long term goal of this research project is to reveal the neural substrates of sensory detection and processing, which has direct relevance to many neurological disorders.